Figure 1.

The Golden Toad, once abundant in Costa Rica, has not been seen since the late 1980s. Photo: U.S. Fishery and Wildlife Service.

Amphibians have been around for over 360 million years, enduring at least three mass extinction events including the one that eliminated the dinosaurs. However, it remains to be seen how they will fare through the current extinction event. A recent Global Amphibian Assessment revealed that

About half of all amphibians are suffering declines.

nearly half of all amphibian species are declining

one-third to one-half are threatened with extinction

over 120 species have become extinct in recent years1

Amphibians seem to be faring worse than other taxa; for every threatened species of bird or mammal, there are two to three species of amphibian threatened with extinction.

Why are amphibians important to our well-being?

They provide vital biomedicines, including analgesics and antibiotics.2 A compound capable of preventing HIV infection has been found in the skin of the Australian red-eyed tree frog (Litoria chloris) and several related species.3

Amphibians are also indicators of environmental health. Trace amounts of the herbicide atrazine in the environment and in our drinking water are capable of chemically sterilizing developing tadpoles.4 Are amphibians modern-day canaries in the coal mine, warning us of worsening conditions that may one day threaten us?

Amphibians are also vital components of their ecosystems, and in some regions a single amphibian species can exceed the biomass of all the bird or mammal species combined.5

Amphibians have also played an important role in human culture, from religion to fables and traditional medicines.6,7

Why are amphibian populations declining?

Amphibian extinctions are caused by diverse factors, with habitat loss as one of the most significant threats impacting 90 percent of those species currently considered threatened. But a recently described fungus, Batrachochytrium dendrobatidis, has been receiving much scientific scrutiny in the past decade.

An infectious chytrid fungus is killing them.

Figure 2.

Southern Corroboree Frog populations, once numerous in Australia, have declined by 80% in the last decade. Photo: Taronga Zoo.

This parasite was previously thought to infect only vascular plants and invertebrates, but now it has been connected to dying amphibians on every amphibian-inhabited continent. For example, scientists have observed how amphibian populations in the mountains of Central America quickly suffered a 50 percent loss of species and an 80 percent loss of individuals after arrival of the fungus, and that the disease is spreading southeast through the isthmus at about 28 kilometers per year.8

The disease cannot be stopped in the wild.

Can the killer fungus be stopped?

It has been posited that amphibian chytrid is native to South Africa where it lives symbiotically with the African clawed frog.9 Since the 1930s, these frogs have been distributed around the world by the tens of thousands, initially for use in human pregnancy tests. Although it is easily treated in captivity, the disease cannot be stopped in the wild, and massive extinctions are predicted as it continues to spread around the world. Amphibian chytridiomycosis has been called “the worst infectious disease ever recorded among vertebrates in terms of the number of species impacted and its propensity to drive them to extinction.”10

The world reacted in 2005 with a response plan.

Although the scientific community has been aware of and is monitoring the developing problem for several decades, intervention has not been a unified priority. In 2005, the global conservation community united and stated, “it is morally irresponsible to document amphibian declines and extinctions without also designing and promoting a response to this global crisis.”4,10 An Amphibian Conservation Summit was convened with the world’s amphibian authorities from academia, zoos, governments, veterinary medicine, and other diverse disciplines. A declaration was produced calling for an Amphibian Conservation Action Plan (ACAP) to address the extinction crisis and establish the Amphibian Specialist Group (ASG) to carry out that plan.11 The ACAP calls for four lines of action:

Research—expand understanding of causes of declines

Assessment—document amphibian diversity and its changes

Conservation—develop long-term conservation programs

Rapid response—intervene against imminent extinctions

It will cost about $400 million.

The overall budget for these initiatives in the first five years is estimated at $400 million. Although this seems like an impossibly large sum, it is less than the cost of two 747 airplanes and just 0.1 percent of the US war budget in the Middle East. It is only about a quarter of what US federal and state agencies currently spend on endangered and threatened species in a year ($1.4 billion), and it’s just three times what these agencies spent on their top recipient, the Chinook salmon ($161,309,500), a single sport and commercial fish species that is being deliberately introduced in parts of North America.

Amphibian survival depends on captive management.

While the ACAP’s greatest conservation priority is in situ action, that is, in the wild (as opposed to ex situ, in a controlled situation such as a lab), some threats like chytrid fungus cannot be addressed in the wild. Without immediate captive management as a stopgap component of an integrated conservation effort, hundreds of species will become extinct. The World Conservation Union, IUCN, has urged that “all critically endangered and extinct in the wild taxa should be subject to ex situ management to ensure recovery of wild populations,” and the ACAP white papers echo that assertion: “Survival assurance colonies are mandatory for amphibian species that will not persist in the wild long enough to recover naturally once environments are restored; these species need to be saved now through ex situ measures so that more complete restoration of ecosystems is possible in the future.”10 Comparable calls to action are included in the Global Amphibian Assessment and other documents.

What can the Amphibian Ark do?

Fortunately, a thriving industry already exists that specializes in captive management of animals. Zoos and related facilities number over 1200 institutions with more than 100,000 employees and attract about 600 million visitors per year. Zoos have the capability to assist with the following:

Zoos already have the means to help amphibians.

rapid response rescues

captive assurance colonies

providing animals for release and research

conservation education

capacity building

fundraising

helping to develop recovery plans

The World Association of Zoos and Aquariums (WAZA) has joined with the Conservation Breeding Specialist Group (CBSG) and ASG to form the Amphibian Ark, or AArk for short. The AArk vision is the world’s amphibians safe in nature. Its mission is to work with partners to ensure the global survival of amphibians, focusing on those that cannot be safeguarded in nature. AArk is rapidly developing capacity to coordinate ex situ programs implemented by partners around the world, with the first emphasis on programs within the range countries of the species. At the same time, it maintains constant attention on its obligation to couple ex situ conservation measures with necessary efforts to protect or restore species in their natural habitats. Its activities include these:

AArk will work with zoos and others on conservation.

provide strategic guidance on activities to all stakeholders, such as zoos, wildlife agencies, universities

lead development and implementation of training programs for building capacity of individuals and institutions

develop communications strategies, messages, and materials to promote understanding and action on behalf of amphibian conservation

The AArk’s Conservation Plan is one part of the comprehensive ACAP; the ex situ component may help stave off many extinctions, but safeguarding these species in situ will be the ultimate measure of success. In 2008, AArk will lead zoos in a globally coordinated public awareness campaign, “The Year of the Frog.” The publicity campaign will help leverage a simultaneous worldwide capital campaign managed at the level of the individual institutions.

What are the challenges?

Zoos can manage only 10 percent of species that need help.

The ex situ conservation community faces many challenges to meet expectations, first and foremost of which is rapidly increasing capacity. It is estimated that the global zoo community can currently manage viable populations of around 50 amphibian species, which amounts to perhaps 10 percent of those requiring ex situ intervention. One solution is to have zoos construct additional biosecure facilities where needed, ensuring that keepers are trained and resources are appropriately allocated to support this action. Of course, some zoos are already making valuable contributions to amphibian conservation. Some are constructing dedicated facilities on grounds, and some are helping to develop facilities in other regions of the world. Zoos are leading dozens of amphibian conservation programs, including habitat restoration, translocations, conservation education and research,12 and region-wide amphibian community rescues.13 There are now several zoo-led courses designed to develop husbandry expertise, including AZA’s amphibian biology and management course, which has spawned similar courses in Mexico, Ecuador, and Colombia.

Amphibians are vitally important as

integral components of ecosystems5

indicators of environmental health4,14

contributors to human health2,3

Amphibians are today’s greatest conservation challenge.

Amphibians persisted as the dinosaurs came and went, but today as many as half of all species are threatened with extinction. We are only just beginning to understand the impacts of their disappearance.15,16 Addressing the amphibian extinction crisis represents the greatest species conservation challenge in the history of humanity. The global conservation community has formulated a response, and an integral part of that response is the Amphibian Ark, in which select species that would otherwise go extinct will be maintained in captivity until they can be secured in the wild. Without immediate captive management as a stopgap component of an integrated conservation effort, hundreds of species may become extinct.

Kevin Zippel, Ph.D., is the program officer for the Amphibian Ark. He worked in the Department of Herpetology at the Wildlife Conservation Society/Bronx Zoo and in the National Amphibian Conservation Center at the Detroit Zoo before moving to his current position. Zippel received his Ph.D. from the University of Florida. http://www.cbsg.org/cbsg/staff/

learnmore links

BioScience Articles

» “Ghosts in Our Midst: Coming to Terms with Amphibian Extinctions.”
A global mass extinction of amphibians is well under way, driven both by habitat loss and by environmental changes. As amphibian communities in Central America are being decimated by chytrid disease, scientists are working to fashion an emergency response. They are also sending out an urgent warning about what the loss of these environmentally sensitive species may portend. Learn more about the decline of the first vertebrates on Earth in the April 2007, BioScience article by Scott Norris. Free to read. http://caliber.ucpress.net/doi/full/10.1641/B570403

» “Amphibian Population Declines: Evolutionary Considerations.”
Numerous factors, such as global environmental changes, habitat destruction, introduced species, diseases, and chemical pollution, appear to be contributing to amphibian population declines. Blaustein and Bancroft (BioScience, May 2007) believe that a better understanding of amphibian population declines requires that scientists and policymakers consider the ecological processes associated with the declines in light of specific evolutionary principles. Free to read. http://caliber.ucpress.net/doi/full/10.1641/B570517

FrogLog Newsletter

Global Amphibian Assessment

Read about the global study of the world’s 5,918 known species of frogs, toads, salamanders, and caecilians. Click on the map to find the status of amphibians in different parts of the world. http://www.globalamphibians.org/

educatorresources

ActionBioscience.org original lesson

This lesson has been written by a science educator to specifically accompany the above article. It includes article content and extension questions, as well as activity handouts for different grade levels.

Lesson Title: Save Our AmphibiansLevels: middle – high school Summary: This lesson engages students in critical thinking about the value of amphibians and encourages them to consider ways to save threatened species. Students create displays, research fun facts and fables, look for “frog penpals”, and more!

Useful links for educators

» Fieldwork
Log on to learn how your students can participate in monitoring amphibians in a wetland near you. There are detailed instructions about how to go “frogging,” forms to download and fill out, and background information. http://www.pwrc.usgs.gov/naamp/

» Case of the Disappearing Frogs
An intermediate-grade lesson plan on the lifecycle of frogs. This is one lesson plan from the Oregon Coast Aquarium’s web page titled Adventures Online, which has other lesson plans and online activities related to the declining amphibians mystery. http://www.aquarium.org/disappearingfrogs/corepage.htm